Hydraulically operated mechanical knee lock



0. S- JOHNSON ET AL HYDRAULICALLY OPERATED MECHANICAL KNEE LOCK Jan. 9, 1951 3 Sheets-Sheet 1 Filed Aug. 5, 1948 B s l O 2 2 262 w e 4 5 l e 6 .4 B I H mm III 1.. H r F. w I 11! 5 v 0 W *w zao m n2n INVENTORS oer/N .5. JOHNSON Fee-0 7: 2065976 Jan. 9, 1951 o. s. JOHNSON ET AL HYDRAULICALLY OPERATED MECHANICAL KNEE LOCK Z Sheets-Sheet 2 Filed Aug. 5, 1948 INVENTORS 0m 5. JOHNSON F250 7". 2056275 Jan. 9, 1951 o. s. JOHNSON ET AL HYDRAULICALLY OPERATED MECHANICAL KNEE LOCK Filed Aug. 5, 1948 3 Sheets-Sheet 3 I: m====i INVENTORS oer/N .9. JOHNSON F250 7: 2086975 7 RTTOENEV Patented Jan. 9, 1951 HYDRAULICALLY OPERATED MECHANICAL KNEE LO CK Orvin S. J ohnson, .ManhattanBeach, and Fred ,T; Roberts Los Angeles, Calif., assignors to N0rthrop Aircraft, Inc., Hawthorne, -Galif a corporation of California Application August 5, 1948, 'Serial No; 42,636

Claims.

The present invention relates generally to artificial legs, and "more particularly to the type of leg used in above-knee amputations, wherein the'lower leg component is connected by a knee joint :to an upper leg component that is attached to the stump. In artificial legs of this class, it is :essential to provide .a means in the knee joint mechanism for locking the knee during certain phases of the walking cycle, so as to preventinvoluntary flexion of the leg.

Locomotion studies of human gait have established the fact that during each complete walking cycle, the natural knee locks in two separate positions; the first being when the :heel strikes the ground at the forward end of the leg swing, andthe second beingat'the rear end of the leg swing, whenthe weight ismomentarily supported onthe toes during the push-off phase. Between the'first and second locked positions, or while the weight of the body is supported on the leg, the knee unlocks andflexes slightly to cushion the shock of impact. One of the principal objects of the invention, therefore, is to duplicate this sequence of actions, and toprovide a mechanism which exerts a positive locking action on the knee when thesheel strikes the ground, and again during the push-off phase when the weight is carried on the toes.

Another object of the invention is to provide a mechanism responsive to the sudden applicationof a force on the heel or toe of the foot, for locking'the knee at any position of flexion, so as to prevent the leg from collapsing under the wearer in the event of stumbling or momentarily losing balance, and thereby give the amputee opportunity to recover.

Still a further object of the invention is to provide a knee lock actuating mechanism which is silent in operation, substantially free from lost motion, and possessed of great flexibility forpu-rposes of installation. This object is accomplished with a novel hydraulic force-transmitting system which is actuated by cam means on the foot, whereby angular displacement of the foot about the ankle, or of the hinged toe portion with respect to the foot, causes a force to be applied to the lock which looks the knee against flexion. The advantages of this arrangement are that the "hydraulic system eliminates the objectionable mechanical noise experienced with linkage; and having no clearancesto take up, is enti're1y free from loose play. Furthermore, the inherent flexibility of a hydraulic transmission system makes it admirably suited to installation in artificial legs, due to the wide variations in length 2 encountered between the ankle and knee of 'differient individuals; Such variations in length I are immaterial to a hydraulic system, and are tion of thefollowing detailed description of "the preferred embodiment thereof, reference :being' had to theaccompa-nying drawingaiwherei-n:

Figure 1 is .a side elevational :view of :anartificial leg embodying the principles of the invention;

Figure 2 is a front elevational view of the same;

Figure 3 is an enlarged vertical section through the knee ,joint,.takensubstantially along theiline 3'3 in Figure :2;

Figure 4 is an enlargedxse'ctionalview through the ankle joint, takenat 4*:4 inFigure 1 Figure 5 is a reduced sectional-.view, taken at 55 in Figure 4, showing the manner in which the knee lock is actuated by plantar flexion of the foot;

Figure 6 isa sectional view, taken at 6:-6 in Figure 4, showing the manner in whichthe knee lock is operated by upward deflection of the hinged toe portion of the foot;

Figure 7 is an enlarged sectional view through the kneejoint, taken at 1-4 in Figure 2; and

Figure 8 is another sectional view throughthe knee, taken at 8-8 in Figure 2.

V In the drawings, the artificial leg, representing the preferred embodiment of the invention is designated in its entirety by reference numeral HI, and isseen to comprise upperand lower leg components ll and I2, respectively, which are connected together by a knee joint l3 for rela-*- tive swinging movement. Attached to the bottom end of the lowerleg component I2 by an ankle joint It is a foot I5 having a hinged toelportion 16. The upper leg component I] may take any desired form .and in the present instance comprises a suction socket 2B of the type which is adapted to be held on the stump by a slight suction pressure within the socket.

Mounted on thebottom end of the suction socket 2'0. in any suitable manner is a base mem her 2! having downwardly extending cylindrical side walls that are cut out in the front and rear to form laterally spaced bracket arms 22 which support the ends of a transversely disposed tubular shaft 23. The shaft 23 has splines or serrations 24 formed in its external surface which extend from one end thereof to the other, and the ends of the shaft are received within serrated holes in the bracket arms 22, so that the shaft is rigidly held against rotation with respect thereto. Cap screws 25 are screwed into the ends of the shaft 23 and engage the outer surfaces of the bracket arms 22 to confine the shaft between the arms. Internally serrated-bearing sleeves (not shown) are inserted over the ends of the shaft 23 adjacent the inner surfaces of the arms 22, and journalled on these sleeves for fore and aft swinging movement is a yoke member 26.

The yoke member 25 has a split-clamp sleeve portion 3b which is inserted over the top end of a pylon tube i of the lower leg component [2, and is securely clamped thereto by bolts 32. The upper portlon of the yoke 26 is bifurcated, forming laterally spaced, upwardly extending arms 33 and 34 which are drilled and bushed to receive the aforementioned bearing sleeves on the shaft 23, The lower leg component l2 need not necessarily be of the pylon construction shown, but might take any other desired form. In the case .Of the pylon construction shown herein, the tube 3i, knee l3, and ankle i4 may be enclosed by a cosmetic shell for the sake of improved.appear-.

ance and to protect the clothing of the wearer.

The. knee joint [3 is adapted to be locked against fiexion under certain conditions, and to this end is provided with a self-energizing, friction lock 35 comprising a brake band 35 and C-shaped, anchor link 31. The brake band 36 encirclesand fits snugly around a tubular shoe or sleeve 4i} which is inserted over the shaft 23 and serrated internally to mesh with the serrati0ns .24. The two ends of the brake band 36 are brought together in a slightly spaced, overlapping relationship, as Shown in Figure 3, and are slotted out at ill and 42 to receive the large .end of the anchor link 3T,.to which they are attached by pins3 and 44. The pins 43 and 44 are spaced apart in a generally radial direction with respect to the axis of shaft 23, for reasons which will be explained shortly.

The small end of the anchor link 3'! is conhosted by a pin 35 to the top end of a link 46, the bottom end of which is swingably connected to a bolt 55 extending transversely between the yoke arms 33, 3d. The link 45 provides a floating anchorage for the anchor link 3?, and enables the brake band 36 and large end of the anchor link, to which it is attached to rotate slightly about the sleeve 40.

The anchor link 3's, in addition to preventing the brake band 35 from turning on the sleeve 40, serves also to clamp the brake band tightly around the sleeve, thereby locking the yoke 25 and its lower leg component E2 to the stationary knee shaft 23. This locking action results when the anchor link 37 is rocked in a counterclockwise direction about its right-hand end (Figure 3), which has the effect of drawing the ends of the brake band 35 together and Wrapping the brake band tightly around the sleeve 40. A cornpression coil sprin 53 that is attached to the underside of the anchor link 31 and bears slidably on the outer surface of the brake band 38, urges the anchor link away from the brake band, which has the effect of rocking the anchor link 4 in a clockwise direction about its right-hand end to release or unlock the brake band from sleeve 45; The lock 35 is actuated by rotating the brake band 35 slightly in a clockwise direction about the sleeve 4! which carries the right hand end of the anchor link 31 downwardly with it. Pins 43 and 44, being fixed to the anchor link 37, move in concentric arcuate paths about pin 45 as a center; and pin 45, in turn, shifts slightly along an arcuate path about pin 5!! as a center to accommodate the change in position of the anchor link. The p ns 43 and 44 are also fixed to the ends of the brake band 35, however, and the rotational movement of the latter is about the axis A of shaft 23 as a center. Hence, there is a conflict in the path followed by pins 43 and 44 as a result of their attachment to both the anchor link 31 and to the ends ofthe brake band 36.

Considering first the path of pins 43, 44 about A as a center, we note that the distance of pin 44 from centerA is slghtly more than half again as much as the distance of pin 43 from center A, which means that the linear travel of pin 4 would have to be approximately half again that of pin 53 if the two pins were to remain in the relative positions as the brake band turns on thesleeve ea. However, the pns 43, 44 are also constrained to swing about pin 45 as a center,

. and in this case the distance of pin 44 from pin 45 is only about one-fourth again as much as the distance of pin 43 from pin 45; hence the linear travel of pin 44 is only one-fourth aga n that of pin 43. Since the pins 43, 44 are immovably fixed to the anchor links 37, it follows that the travel of pin 44 with respect to pin 43 is governed by the anchor link, and this means that the travel of pin 44 with respect to that of pin 43 is less than the amount required to maintain the two pins in the same relative position with respect to the brake band. The net result is that when the brake band 36 is rotated in a clockwise d'rection about the sleeve 49, the pin 53 moves downwardly with respect to pin 44, which causes the brake band to wrap tightly around the sleeve and thereby lock the knee against flexion. One characteristic of this type of lock is that it is self-energizing in nature, and therefore tends to look more .tightly as the load on the knee joint is increased.

The lock 35 is held in the released or unlocked condition by means of a compression coil spring 52 which encircles a bolt 53 and bears at its bottom end against a bracket 54 that is secured by bolt 55 to the arms of yoke 28 at the back side thereof. The top end of spring 52 bears upwardly against the bight of a U-shaped clevis 56 which is fastened to the extended ends of pin 45. Bolt 53 passes through holes 6% and 5! in the clevis 56 and bracket 54, respectively, and is free to slide through either of the same when the spring 52 is compressed. A nut 52 is screwed onto the bottom end of bolt 53 and engages thebracket 54 to limit the upward travel of the bolt,

The lock 35 is adapted'to'be operated by a hydraulic actuating mechanism consisting of a work cylinder 55 and a hydraulic master cylinder 66 which are connected together by a fluid line 61 of aluminum tubing or the like. The cylinders 65 and 68 may take any desired form, but are'preferably of the construction illustrated, embodying thin-walled, flexible metal bellows 68 and B9 of the type known as fSylphon bellows, which provide a leak-proof, closed system. The bellows 68 of the work cylinder'55 is contained Within a cylindrical chamber 10 in a housing TI, and the latter is secured by bolts 12 to yoke member 26 between the arms 33, 3s thereof.- One end of the bellows 68 is soldered to a plug I3 which is screwed into the bottom end of the chamber Ill. The top end of the bellows is soldered to a movable member I4 having an upwardly extending cylindrical stem I5 which extends through and is slidable within a bore 76 in the top end of the housing.

Extending part wa down into the stem '15 along the axis, thereof is a tapped hole 80', into which an eye bolt SI is screwed. Ehe eye bolt 8i has a horizontally elongated aperture 82 formed in its top end, and a pin 83 extends through the slot to connect the eye bolt to the front end of a lever arm 84. The lever arm 84 is pivoted intermediate its ends on a transverse pivot bolt 85, and therear end of the lever arm is connected by a pin 86 to an upwardly extending link 96. The top end of the link 95 is attached to the brake band 36 by a pin 9I, which is located so that a downward pull of the link 96 causes the brake band to rotate in a clockwise direction about its supporting sleeve. Thus, the brake 35 i actuated to lock the knee against flexion when the bellows 68 of the work cylinder 55 is expanded, causing the movable member I5 to move upwardly and thereby pulling the link 9E9 downwardly to rotate the brake band in a clockwise direction. The plug I3 closing the bottom end of th bellows chamber It is provided with a tapped hole 92 opening into the bellows 6B, and screwed into this hole is the threaded stud Q3 of a pipe coupling member 95. The tubing 5? extends downwardly from the cylinder 65 and around to the back of pylon 3 I, where it is connected at its bot,- tom end by an elbow fitting 35 to the end of the housing 86 of master cylinder 66.

The cylinder housing 96 is disposed between two laterally spaced, vertical flanges 37 which are formed integral with and extend rearwardly from an ankle yoke 98 mounted on the bottom end of the pylon tube 3!. The flanges 91 are formed with enlarged bearing bosses 99 in their lower ends, and these are drilled to receive a transverse ankle pivot shaft IMF. The shaft I66 extends beyond the bearing bosses Q9, as shown in Figure and its ends are journalled in bushings I 6! which are pressed into apertures in the arms I62 of a U-shaped bracket I 03. The bracket I 63 is disposed within a cavity I64 in the foot I5, and is provided with a downwardly extending threaded stud I85 which extends through a hole I06 in the foot and is secured b a nut Iil'I.

At the front end of the yoke member 9% between the flanges 9? is an upwardly inclinedshelf Ilil which is engageable with the top end of a rubber instep bumper I II that is set into a slight recess in the top surface of a shelf portion II2 of the foot. A horizontal shell I I3 at the rear end of the yoke 98 is engageable with the top end of a rubber heel cushion lid. Th two cushions III and IM engage their respective shelves to locate the foot in its normal position, as shown in Figure 1. The instep cushion III, being rather short, permits only a very limited amount of dorsiflexion of the foot, while the heel cushion H4, being considerably longer, is more resilient and permits a greater degree of plantar flexion.

The housing 96 of the master cylinder 65 is secured to the flanges 9'! of the ankle yoke 98 by two bolts I IS in an upwardly and rearwardly inclined position, with its axis intersecting the axis or the ankle shaft I96. A cylindrical chamber H6 is formed in the housing 96, and the bellows 69 i disposed therein. The top end of the cham- 9 ber is threaded internall to receive ass-rewthreaded plug I26 which, in turn, is provided with a tapped hole I I9 opening into the interior of the bellows 63, that receives the threaded stud I2 I' of the elbow fitting 95. The top end of the bellows 69 is soldered to the plug I26, and the bottom end of the bellows is soldered to a movable member I22 having a stem I23 which extends down through an opening I2 l in the bottom end of the housing. The movable member I22 has a tapped hole extending part way upfrom the bottom end thereof, andscrewed into this hole is the threaded shank of a yoke member I25.

Thelower end of the yoke I25 is bifurcated to provide two laterally spaced armsthat aredrilled to receive a transverse shaft I26, the ends of which project beyond the yoke arms and are slidably disposed within guide slots I30 in a cylindrical extension I3I of the housing 96. Journalled on the shaft I26 between the arms of yoke I25 is a cam follower roller I32 which rides on the peripheries of two cams I33 and I34 that are arranged side by side on shaft I00.

Cam'- I'3'3 is preferably of the configuration shown in Figure 5, and is provided with an arm portion I35 which is secured by a screw I36 to a bracket Me projecting upwardly from the bottom of the cavity I63- in the foot. The aperture in arm I35'through which the screw I36 projects is pref: e-rably slotted, as shown, to permit a limited amount of angular adjustment of the cam about theshaft IN. A. lobe I'M on the periphery of the cam I33 is normally located just below the axis of the master cylinder 66 when the foot is positioned as shown in Figure I, so that the roller I32 bears on the low" portion of the cam immediately at the foot of the rise leading up tothe t op'ofilobe- I iI. Being attached to the foot I5,

the cam I33 is constrained to rotate with the foot about the shaft me when the foot is deflected in plantar flexion, as shown in Figure 5. This is the condition which is obtained when the weight is thrown on the heel at the end of the forward swing phase of the leg during the walking cycle. As the cam I33 rotates with the foot, the-lobe It! raises the roller I32 and compresses tlnbel lows 63, which forces fluid through the line"6I toth-e bellows 63 and causes the latter to expand, thereby operating the lock 35.

Cam I34 is journall'e'd for rotation on shaft I00 and is connectedby a pin I 4? to the rear end of a turn buckle link I45; the front end of said'link being connected by a pin M8 to a bracket I46 on the hinged toe portion I6. The toe portion I'Gis connected to the foot I 5 by a'transverse hinge Iiitjat thebottom of the foot, and is free to be deflected upwardly, as in Figure 6, when the weight of the body is momentarily supported the toes during the push-off phase of the walking cycle. As the toe portion I6 deflects upwardly the bracket member I46 swings in a clockwise directionabout the hinge H58, pushing the turn buckle link I45 to the right, and thereby rocking the cam I34, in a clockwise direction. "The cam IM-is provided with a lobe portion IE'I which is normally positioned just ahead of the roller I32, 'or in a counterclockwise direction with-respect thereto, as seen in Figures 5 and 6, so the roller is positioned on the low portion of the cam at the foot of the incline leading to the top of the lobe IBI. Thus, when the toe portion I6 is deflected upwardly, the cam I35 is rocked in a clockwise direction, causing the roller I32 to ride up onthe lobe I 5I, and thereby compressing the 55 bellows' ts to operate th lock 35,

From the foregoing description, it will be seen that the bellows 69 of the master cylinder 66 is normally fully extended when the foot I and toe portion I6 are in their normal positions, as shown in Figure 1, and is compressed either when the foot I5 is displaced in plantar flexion, or when the toe portion I6 is deflected upwardly. In the one case, compression of the bellows 69 is caused by roller I32 riding up onto lobe I4I of cam I33; ,while in the other case, the roller rides up onto lobe I5I of cam I3-I. Such compression of the bellows 69, of course, produces a corresponding extension of the bellows 68 in the workcylinder 65, thereby operating the lock 35. Wedge-shaped cushions I52 of sponge rubber or other resilient material are disposed between the adjacent faces of the toe portion I6 and foot I5 on opposite sides of the bracket I46 to provide resilient bumpers for yieldingly holding the toe portion I5 in extended position.- These bumpers I52 are .compressed when the toe portion I6 is deflected upwardly, as in Figure 6.

In order to simulate more closely the forward swinging rate of the natural leg during the walking cycle, we have embodied a friction brake I60 in the knee joint I3, which serves to check or slightly retard the free forward swinging movement of the lower leg with respect to the upper leg. The friction brake I60 comprises a split brake band I6I that encircles the sleeve 40 alongside the lock 35. The brake band I6I is provided with an ear I62 having an open-end slot I53 formed therein, extending radially from the axis of the knee shaft; and disposed within this slot is an anchor pin I64 which projects inwardly from the yoke arm 3 and prevents the brake band from turning. At the top of the brake, the two ends of the brake band I6I are turned outwardly to form ears I65 and I66 which are connected by an adjusting screw I10. The screw I10 extends through a smooth hole in the ear I65 and is threaded into atapped hole in ear I 65, so that when the screw is turned, the ears I65, I56 are drawn together or spread apart to increase or decrease the tension of the brake band on the sleeve 40.

On the opposite sides of the lock 35 from friction brake IE0 is a limit stop member I12, shown to best advantage in Figure 8. The member I12 has a serrated hole I13 formed therein which receives the serrated shaft 23, whereby the two members are locked together against relative rotation. Two angularly related shoulders I14 and I15 are provided on the member I12, and these are respectively engageable with a resilient bumper strip I18 lying on a horizontal shelf I80 on the yoke arm 33, when the lower leg'is in the solid-line xtended position, or in the fully flexed position shown in phantom line. It might be mentioned at this point that when the leg is fully extended, the axis of the hinge pivot is located posterior to the vertical line of the center of gravity of the body, causing the pivot to go past the centerline as the leg is extended, giving about 2 of hyper-extension, which stabilizes the knee joint.

It is believed that the construction and operation of the mechanical knee lock and its hydraulic actuating mechanism will be fully understood from the foregoing description, and that the many advantageous features thereof will be readily appreciated by those skilled in the art. While we have shown and described in considerable detail what we believe to be the preferred form of our invention, it is to be understood that such details are not restrictive, and that various changes may be made in the shape and arrangement of the several parts without departing from the broad scope of the invention, as defined in the appended claims.

We claim:

1. In an artificial leg having an upper leg component, a lower leg component swingably connected thereto by a knee joint, and a foot pivotally connected to said lower leg component by an ankle joint, the combination of a mechanical friction lock operatively connected to said knee joint to lock the same against flexion movement,

- a hydraulic work cylinder mounted on one of said legcomponents and connected to said lock to operate the same, and a hydraulic master cylinder mounted on said lower leg component and connected by a fluid line to said work cylinder, said master cylinder being mechanically linked to said foot sothat pivotal movement of the foot about said ankle joint from a redetermined normal position causes said master cylinder to be compressed, thereby applying fluid pressure to said work cylinder to operate the lock.

2. In an artificial leg having an upper leg component, a lower leg component swingably connected thereto by a knee joint, and a foot pivotally connected to said lower leg component by an ankle joint, the combination of a mechanical friction lock operatively connected to said knee joint to lock the same against flexion movement, a, spring attached at one end to one of said leg components and operatively connected at the other end to said look so as to exert a pressure thereon tending to release the lock, and hydraulic actuating means operatively connected to said lock in opposition to said spring, said actuating means including a hydraulic work unit and a fluid pressure generator, both mounted on said lower leg component, said fluid pressure generator being mechanically linked to said foot so that the fluid pressure in the system is increased when said foot is pivoted about said ankle joint from a predetermined normal position, and said work unit being operable to overcome said spring and lock said knee when the fluid in the system exceeds a predetermined pressure.

3. In an artificial leg having an upper leg component, a lower leg component swingab-ly connected thereto by a knee joint, and a foot pivotally connected to said lowe leg component by an ankle joint, the combination of a mechanical friction lock operatively connected to said knee joint to lock the same against fiexio-n movement, a hydraulic work unit mounted on one of said leg components and comprising an expansible chamber having a movable member connected to said lock to operate the same, another hydraulic unit mounted on said lower leg component and comprising an expansible chamber having a movable member, a fluid line connecting the expansible chamber of said last-named unit with that of said first-named unit, a cam member fixedly mounted on said foot for angular movement therewith about said ankle joint, and a follower engaging said cam and operatively connected to said movable member of said last-named hydraulic unit, said cam member being so designed that angular displacement of said foot about said ankle joint from a predetermined normal position causes said follower to compress said chamber of said last-named unit with corresponding extension of the chamber of said first-named unit to operate said lock.

4. In an artificial leg having an upper leg com- 'p'onent, a lower 'le'gcomponent swingably connected thereto by a knee joint, a foot pivotally connected to said lower leg component by an ankle joint, and a hinged toe portion on the front end of said foot, the combination of a mechanical friction lock operatively connected to said knee joint to lock the same against flexion moveinent, and hydraulic actuating means for operating said lock responsive to angular displacement of said toe portion about its hinge axis from the normal position, said actuating unit including a hydraulic work unit and a fluid pressure generator, both mounted on said lower leg component, said .fluid pressure generator being mechanically linked to said toe portion so that the fluid pressure in the system is increased when said toe ortion is bent upwardly about its hinge axis, and said work unit being operable to lock said friction look when the fluid pressure in the system exceeds a predetermined pressure.

5. In an artificial leg having an upper leg component, a lower leg component swingably connected thereto by a knee joint, a foot pivotally connected to said-lower leg component by an ankle joint, and a hinged toe portion on the front end of said foot, the combination of a mechanical friction lock operatively connected to said knee joint to lock the same against flexion movement, a hydraulic wo a: cylinder mounted on one of said leg components and connected to said lock to operate the same, and a hydraulic master cylinder mounted on said lower leg component and connected by a fluid line to said work cylinder, said master cylinder being mechanically connected to said toe portion in a manner such that hydraulic pressure in the system is increased when said toe portion is deflected upwardly about its hinge axis from the normal position.

6. In an artificial leg having an upper leg component, a lower leg component swingably connected thereto by a knee joint, a foot pivotally connected to said lower leg component by an ankle joint, and a hinged toe portion on the front end of said foot, the combination of a mechanical friction lock operatively connected to said knee joint to look the same against flexion movement, a hydraulic work cylinder mounted on said lower leg component and connected to said lock to operate the same, a hydraulic master cylinder mounted on said lower leg component and connected by a fluid line to said work cylinder, a rotatable cam member coaxial with said ankle joint and connected to said hinged toe portion, whereby angular movement of said toe portion about its hinge axis causes said cam member to rotate, and a follower engaging said cam and operatively connected to said master cylinder to actuate the same, said cam member being designed so that said work cylinder is compressed by said follower when said toe portion is deflected upwardly about its hinge axis, thereby operating said lock.

7.1n an artificial leg having an upper leg component, a lower leg component swingably connected thereto by a knee joint, a foot pivot ally connected to said lower leg component by an ankle joint, and a hinged toe portion on the front end of said foot, the combination of a mechanical friction lock operatively connected to said knee joint to lock the same against flexion movement, a hydraulic work cylinder mounted on said lower leg component and connected to said lock to operate the same, a hydraulic mas er cylinder mounted on said lower leg component and connected by a fluid line to said work cylinder, rotatable cam means coaxial with said ankle joint and connected to said foot and to said hinged toe portion, and a follower engaging said cam means and operatively connected to said master cylinder, said cam means being designed so that said work cylinder is compressed by said follower when said foot is deflected angularly about said ankle joint from a predetermined normal position, or when said toe portion is bent upwardly about its hinge axis, thereby operating said lock.

8. In an artificial leg having an upper leg component, a lower leg component swingably onnected thereto-by a knee joint, a foot pivot-' ally connected to said lower leg component by an ankle joint, and a hinged toe portion on the front end of said foot, the combination of a me chanical friction lock operatively connected to said knee joint to lock the same against flexionl movement, a hydraulic work cylinder mounted on said lower leg component and connected to said lock to operate the same, a hydraulic master cylinder mounted on said lower leg component and connected by a fluid line to said work cylinder, rotatable cam means mounted coaxial with the pivot axis of said ankle joint, said cam means being constrained to rotate with said foot when the latter is flexed, and being connected to said hinged toe portion for movement therewith when the toe portion is deflected upwardly about its hinge axis, and a follower engaging said cam means and operatively connected to said master cylinder, said cam means being so designed that said work cylinder is compressed by said folower when said foot is deflected angularly about said ankle joint from a predetermined normal position, or when said toe portion is deflected upwardly about its hinge axis, thereby operating said lock.

9. In an artificial leg having an upper leg component, a lower leg component swingably connected thereto by a knee joint, a foot pivotally connected to said lower leg component for rotation about a transverse anke shaft, and a hinged toe portion on the front end of said foot, the,

combination of a mechanical friction lock operatively connected to said knee joint to lock the same against flexion movement, a hydraulic work cylinder mounted on said lower leg component and connected to said lock to operate the same, a hydraulic master cylinder mounted on saidlower leg component and connected by a fluid line to said work cylinder, a pair of cams arranged side-by-s'ide on said ankle shaft, one of said cams being connected to said foot so as to rotate therewith when the foot is deflected, the

other of said cams being journaled for rotation on said ankle shaft, link means connecting said other cam to said hinged toe portion, whereby said other cam is rotated when said toe portion is rotated about its hinge axis, and a follower engaging both of said cams and operatively' connected to said master cylinder, said cams being designed so that said master cylinder is compressed by said follower when said foot is rocked about said ankle shaft from a predetermined normal position, or when said toe portion is deflected upwardly about its hinge axis, thereby operating said lock.

10. In an artificial leg having an upper leg for swinging movement on said knee shaft, a foot pivotally connected to said lower leg component I01 rotation about a transverse ankle shaft, and

a hinged toe portion on the front end of said foot, the combination of a self-energizing mechanical friction lock comprising a brake band encircling said knee shaft, an anchor link attached at one end to said lower leg component, both ends of said brake band being attached to the other end of said anchor link at points spaced apart in a generally radial direction relative to said knee shaft, said brake band tending to bind tightly around said knee shaft when said other end of said anchor link is moved in one direction about the knee shaft, and to release said knee shaft when moved in the other direction, a spring acting on said other end of said anchor link and urging the same in said other direction, a thin-walled, flexible metal bellows having a movable member at one end thereof connected to said brake band, whereby extension of said bellows causes said other end of said anchor link to move in said one direction against the pressure of said spring to operate said lock, another thin-walled, flexible metal bellows mounted on said lower leg component and connected by a fluid line to said first-named bellows, said las named bellows having a movable member at one end thereof, a pair of cams arranged side-by-side on said ankle shaft,one of said cams being connected to said foot so as to rotate therewith, the other of said cams being journaled on said shaft for rotation with respect to said foot, link means connecting said other cam to said hinged toe portion, and a follower engaging both of said cams and connected to said movable member of said last-named bellows, whereby said last-named bellows is compressed by said cams responsive either to angular deflection of said foot about said ankle shaft or to upward deflection of said toe portion about its hinge axis, said compression of said last-named bellows causing said first-named bellows to extend and thereby operate said lock.

ORVIN S. JOHNSON.

FRED T. ROBERTS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS- Number Name Date 2,175,136 Stewart Oct. 3, 1939 2,442,530 Eberle et a1 June 1, 1948 FOREIGN PATENTS Number Country Date 530,887 France Oct. 12, 1921 OTHER REFERENCES Research Reports on Artificial Limbs, by Committee on Prosthetic Devices, National Research Council. A copy was received in Div. of the Patent Office June 6, 1946. Pages 21 and 22. 

